1. Technical Field
The present disclosure relates to a hydraulic lash adjuster with a damping device for use in an internal combustion engine valvetrain.
2. Background Art
Modern valvetrain systems use hydraulic lash adjusting elements to compensate for valve train wear, thermal expansion during engine warm-up, and any other phenomena that change clearances within the valve train mechanical linkage. Hydraulic lash adjusters use hydraulic fluid within a variable volume pressure chamber behind a plunger to transmit the valve actuating force from a camshaft to the rocker arm. The volume of fluid within the chamber changes to move the plunger and remove the clearance or lash within the mechanical linkage of the valvetrain. Under some operating conditions or in particularly compliant valvetrains, the lash adjuster may “pump-up” or over compensate by allowing too much hydraulic fluid into the pressure chamber during events where rapid unloading of the mechanical linkage occurs. If the duration of the unloading event is longer than the time required for the lash adjuster to respond and increase the hydraulic fluid volume within the high pressure chamber, the lash adjuster may prevent the valve from closing properly, which could result in undesirable operation or engine damage. Conventional lash adjuster design does not allow for explicit control of the damping characteristics of the adjustment system. Instead, the system response is dictated by the geometry and design of the passage between the high and low pressure chambers within the lash adjuster. While this approach may be suitable for many applications, it may be difficult to tune or adapt the response to a particular valve train system.